A relationship between two organisms in which one benefits and the other is unaffected is called what?

• A. Parasitism
• B. Mutualism
• C. Commensalism
• D. Predation

Answer: (C)

The situation describes a one-sided benefit where the other organism is left essentially unchanged, which is commensalism. In this type of relationship, one partner gains something valuable—such as food, shelter, or a means of transportation—while the other does not receive a benefit and is not harmed. A classic example is barnacles that attach to a whale: the barnacles get a convenient place to live and access to plankton-rich water as the whale moves, while the whale is largely unaffected. This contrasts with parasitism, where the host is harmed; mutualism, where both organisms benefit; and predation, where one benefits by consuming the other. So, the term that best fits the described interaction is commensalism.